1. Field of the Invention
The present invention relates to the field of manufacturing integrated circuits and, more particularly to an apparatus for controlling the flow of process material into a thin film deposition chamber.
2. Description of the Background Art
Chemical vapor deposition (CVD) processes are widely used to deposit material layers on semiconductor devices and integrated circuits. These CVD processes deposit material layers on semiconductor devices and integrated circuits by reacting gaseous precursors adjacent to the surfaces thereof. The reaction rate for CVD processes is controlled via temperature, pressure and precursor flow rates.
Some precursors are derived from low vapor pressure liquids. The low vapor pressure liquids are transported using a bubbler (or boiler). The bubbler includes an ampoule containing a source of the liquid precursor. A carrier gas provided to the ampoule saturates the liquid precursor and transports the vapor to a process chamber. The amount of vapor transported depends on the process chamber pressure, the carrier gas flow rate, as well as the vapor pressure in the ampoule containing the source of liquid precursor. As such, the flow rate of vaporized precursor is difficult to control, which decreases the quality of material layers produced therefrom.
Additionally, liquid precursor shut-off is problematic due to residual liquid precursor in the lines between the ampoule and the process chamber. This residual liquid precursor may be continuously leaked into the process chamber after shut-off resulting in chamber and/or substrate contamination.
Thus, there is a need to provide an apparatus for improved control of a liquid precursor to a process chamber.